Technologies underpin economic and industrial advances and improvements in healthcare, education and societal and public infrastructure. Technologies of the future depend on scientific breakthroughs of the past and present, including new knowledge bases, ideas, and concepts. The proposed international network of interdisciplinary centre-to-centre collaborations aims to drive scientific and technological progress by advancing and developing a new science platform for emerging technology - the optical frequency comb (OFC) with a range of practical applications of high industrial and societal importance in telecommunications, metrology, healthcare, environmental applications, bio-medicine, food industry and agri-tech and many other applications. The optical frequency comb is a breakthrough photonic technology that has already revolutionised a range of scientific and industrial fields. In the family of OFC technologies, dual-comb spectroscopy plays a unique role as the most advanced platform combining the strengths of conventional spectroscopy and laser spectroscopy. Measurement techniques relying on multi-comb, mostly dual-comb and very recently tri-combs, offer the promise of exquisite accuracy and speed. The large majority of initial laboratory results originate from cavity-based approaches either using bulky powerful Ti:Sapphire lasers, or ultra-compact micro-resonators. While these technologies have many advantages, they also feature certain drawbacks for some applications. They require complex electronic active stabilisation schemes to phase-lock the different single-combs together, and the characteristics of the multi-comb source are not tuneable since they are severely dictated by the opto-geometrical parameters of the cavity. Thus, their repetition rates cannot be optimised to the decay rates of targeted samples, nor their relative repetition rates to sample the response of the medium. Such lack of versatility leads to speed and resolution limitations. These major constraints impact the development of these promising systems and make difficult their deployment outside the labs. To drive OFC sources, and in particular, multi-comb source towards a tangible science-to-technology breakthrough, the current state of the art shows that a fundamental paradigm shift is required to achieve the needs of robustness, performance and versatility in repetition rates and/or comb optical characteristics as dictated by the diversity of applications. In this project we propose and explore new approaches to create flexible and tunable comb sources, based on original design concepts. The novelty and transformative nature of our programme is in addressing engineering challenges and designs treating nonlinearity as an inherent part of the engineering systems rather than as a foe. Using the unique opportunity provided by the EPSRC international research collaboration programme, this project will bring together a critical mass of academic and industrial partners with complimentary expertise ranging from nonlinear mathematics to industrial engineering to develop new concepts and ideas underpinning emerging and future OFC technologies. The project will enhance UK capabilities in key strategic areas including optical communications, laser technology, metrology, and sensing, including the mid-IR spectral region, highly important for healthcare and environment applications, food, agri-tech and bio-medical applications. Such a wide-ranging and transformative project requires collaborative efforts of academic and industrial groups with complimentary expertise across these fields. There are currently no other UK projects addressing similar research challenges. Therefore, we believe that this project will make an important contribution to UK standing in this field of high scientific and industrial importance.

Standard multi-kW fibre lasers are now considered 'commodity' routinely produced by multiple manufacturers worldwide and are widely used in the most advanced production lines for cutting, welding, 3D printing and marking a myriad of materials from glass to steel. The ability to precisely control the properties of the output laser beam and to focus it on the workpiece makes high-power fibre lasers (HPFLs) indispensable to transform manufacturing through adaptable digital technologies. As we enter the Digital Manufacturing/Industry 4.0 era, new challenges and opportunities for HPFLs are emerging. Modern product life-cycles have never been shorter, requiring increased manufacturing flexibility. With disruptive technologies like additive manufacturing moving into the mainstream, and traditional subtractive techniques requiring new degrees of freedom and accuracy, we expect to move away from fixed, 'fit-for-all' beams to 'on-the-flight' dynamically reconfigurable 'shaped light' with extensive range of beam shapes, shape frequency and sequencing, as well as 3D focus steering. It is also conceivable that the future factory floor will get 'smarter', undergoing a rapid evolution from dedicated static laser stations to robotic flexible/reconfigurable floorplans, which will require 'smart photon delivery' over long distances to the workpiece. Such a disruptive transition requires a new advanced generation of flexible laser tools suitable for the upcoming 4th industrial revolution. Light has four characteristic properties, namely wavelength, polarization, intensity, and phase. In addition, use of optical fibres enables accurate control and shaping in the spatial domain through a variety of well-guided modes. Invariably, all photonic devices function by manipulating some of these properties. Despite their acclaimed success, so far HPFLs are used rather primitively as single-channel, single colour, mostly unpolarised and unshaped, raw power providers and remain at a relatively early stage (stage I) of their potential for massive scalability and functionality. Moreover, further progress in fibre laser power scaling, beam stability and efficiency is hindered by the onset of deleterious nonlinearities. On the other hand, the other unique attributes, such as extended 'colour palette', extensively controllable polarisation and beam shaping on demand, as well as massive 'parallelism' through accurate phase control remain largely unexplored. Use of these characteristics is inherent and comes natural to fibre technology and can add unprecedented functionality to a next generation of 'smart photon engines' and 'smart photon pipes' in a stage II of development. This PG will address the stage II challenges, confront the science and technology roadblocks, seek innovative solutions, and unleash the full potential of HPFLs as advanced manufacturing tools. Our aim is to revolutionise manufacturing by developing the next generation of reconfigurable, scalable, resilient, power efficient, disruptive 'smart' fibre laser tools for the upcoming Digital Manufacturing era. Research for the next generation of manufacturing tools, like in HiPPo PG, that will drive economic growth should start now to make the UK global leaders in agile laser manufacturing - enabling sustainable, resource efficient high-value manufacturing across sectors from aerospace, to food, to medtech devices and automotive. In this way the UK can repatriate manufacturing, rebalance the economy, create high added-value jobs, and promote the green agenda through efficient manufacturing. It will also enhance our defence sovereign capability, as identified by the Prime Minister in the Integrated Review statement to the House of Commons in November 2020.